The biggest boogie-man here aren't the corporations in the end.
They may use the system to milk you but that's basically it.
The worst risk in allowing third parties regulate your data is that the government will start to use it for thier purposes. One day they may pass a bill that makes having pornography on your computer illegal. Delete. Just one example..
That would suck wouldnt it? We all love pr0n.
The intelligence agencies may use it to eavesdrop your activities and covertly manipulate or destroy data on your computer if they don't approve what you're doing etc. etc. Saves them the trouble of tapping into anything, they'll just use the built in functions to monitor you.
The system allows 'digital 1984' to happen. It allows Big Brother in a major way. Actually it's THE tool to make it happen.
This is what I worry in the end.
Never before has there been a medium for corporations or governments to access your everyday routines without you knowing or most important without our consent. Never before have they been able to manipulate your files, papers whatever without you knowing (well unless agents actually came to your house, broke in and did it..) or without your consent.
How do they define which MP3's are illegal? What if you make your own music and pack them with mp3? How do you ensure privacy of your home movies if a third party has access to them? They'll have to view them to judge if they're legal or not

There's no way in hell that the day won't come when the RIAA worker who's in charge of evaluating 'suspicious' files will find your home movie so good he can't help but share it with his closest friend. And only with him/her of course.
If the tool is there, sooner or later someone is going to make use of it. Maybe it will start with tracking terrorists.. Then they find it useful to track down major criminals.. Before you know it the agency has tapped in every computer linked in the states and they actively search anti-government etc. data from your computers. You might be blacklisted for making a joke etc.
Hell, they're already doing it through the net traffic.
I've seen what constant spying and constant loss of freedom of speech does and in my opinnion this progress clearly opens up dark visions.
Or maybe things will keep simple: We'll have one palladium machine which we use to do net transactions, buy music movies, shop hardware etc.. And then we'll have one non-palladium machine which we use for private stuff.
The trouble is that RIAA is lobbying to implement mandatory copy protection systems to ALL hardware. I have no idea how that will work or affect our privacy. I'm just suspicious it won't have a positiove effect.